As you progress in Terraria, the world begins to transform during different stages in the game. Amongst these transformations is the spread of biomes, i.e., Evil Biomes. These infestations will become a menace if left untended. We will focus on the Crimson spread in this article and discuss whether it spreads or not in Terraria.
The Crimson biome DOES spread in Terraria. It slowly infects certain nearby tiles and converts them to Crimson variants. With enough Crimson infestation spread (200 to 300 tiles), the whole area changes to the Crimson theme and background and will be considered part of the Crimson biome.
Let’s get into the details of the Crimson biome and its different variants, and also see how it spreads in Terraria.
Crimson Biome
As seen above, or you must have run into it, the Crimson Biome is one of the three evil biomes in Terraria. As the name suggests, this biome has a red theme with fleshy/bloody growth and eyeballs popping everywhere.
If not specially selected, then there is a 50:50 chance of either this or the Corruption biome sprouting in a randomly generated world.
The Crimson biome has its own set of distinct enemies, items, blocks, and even special loot that is unique to this environment. The environment itself is much more hostile to the player as there are thorny bushes all around, and the enemies are much stronger.
Does Crimson Spread?
Unlike other normal biomes, Evil biomes, including the Crimson biome, spread to other areas in the world. This biome will slowly transform certain tiles adjacent to them. This transformation will soon change the whole area into the respective biome itself. The way it spreads is quite random, but there are specific rules that it follows.
Pre-Hardmode and Hardmode Crimson Spread
Crimson Biome will spawn as soon as the world generates and also starts to spread, although it is much slower. The speed of the infection will be greatly increased after defeating the Wall of Flesh boss. However, once you have defeated Plantera, the speed of the infection will be reduced by half.
While in Pre-Hardmode, Crimson will only spread to grass, jungle grass, and thorny bushes. Subsequently, in Hardmode, new and other tiles will also start to infect others. These include:
| Pure Tile | Crimson Variant |
| Grass | Crimson Grass |
| Stone Block | Crimstone Block |
| Ice Block | Red Ice Block |
| Sand Block | Crimsand Block |
| Hardened Sand Block | Hardened Crimsand Block |
| Sandstone Block | Crimsandstone Block |
| Jungle Grass | Crimson Jungle Grass Crimson Grass |
| Jungle Thorny Bushes | Crimson Thorny Bushes |
Crimson Spreading Rules
The game keeps randomly updating tiles after a particular time. Above-ground tiles get updated about six times as often as below-ground tiles, so biome spread will be that much faster above ground. This is an approximation, as the biome/corruption needs to be near the “pure” tiles before it can spread.
When a tile gets infected, it will become a source to infect other tiles around it. Any of the infectious tiles will have a corruptible radius of 7×7 tiles from the center meaning 3 tiles in any direction of the tile is susceptible to crimson infection.
Crimson Grass will spread to any grass right next to it. It doesn’t follow the normal rules of spread. You can artificially spread Crimson using Crimson Seeds, Vicious Powder, Blood Water, or the Clentaminator with Red Solution.
Crimson spread does become a menace, and if left unchecked, it can very likely spread to the whole world. There are ways of completely curing the world of this infection. If you really want the loot from this biome then let it spread otherwise it is recommended to clear ASAP.